Headlight.



M1. FORD.

, HEADLIGHT. APPLICUION FILED AUG. 23. 1915- RENEWED MAR-'12. 1,235,674.

Patented Aug.

ATTORNEYS.

UNITED srarss PATENT OFFICE.

' ARTHUR H. Form,- or IOWA cI'rY, IOWA.

' HEADLIGHT.

Specification of Letters Patent Application filed August 23, 1915, Serial No. 47,001. Renewed March.12, 1917. serial No. 154,338.

To all whom it may concern: v

Beit .known that I, Arum-ion H. Form, a citizen of the United States, residing at IowaCity, in the county of Johnson and State of Iowa, have invented new and useful Improvements in Headlights, of which the following 1s a speclfication.

My invention relates to that class of lamps known as headlights; such as are used commonly on automobiles, and street years. It has for its object the decrease in mounted in a metal case with a glass front.

The result of this arrangement of the parts is that an intense beam of light is thrown along the axis of the reflector. .VVhen the light source is a point and the reflector a perfect par'aboloid of revolution, with the light source at its focus,- the beam is parallel. When the light source is between the mirror and its focus the beam is divergent. When the focus is between the light. source and the mirror, the beam is convergent between the reflector and apoint a distance in front of the reflector .depending on the relation between the focal distance of the reflector and the distance of the light source from it. Beyond the point of convergence I the beam is divergent. Such a beam will be called a crossed beam in the following discussion.

The light source most commonly used at present is an incandescent electric lamp having a spiral filament so placed that the axis of the filament is coincident with the axis of the mirror and so held that the position of the lamp is adjustable along this axis. This kind of an arrangement will be assumed in the following explanations; though. my improved device is.not confined in its applica-I tion to the use of such a lightsource or i 'the'filament ahead of the focus of the remethod of mounting the lamp.

The ordinary requirements of the illumi-' nation from a headlight are that the-center of th'e'beam shall be the brightest portion;

thebeam shall be divergent or crossed; and shall be thrown well aheadof the vehicle which carries. the light.

of the filament substantially .at the, focus'of the mirror with the rest of the filament between the mirror and its focus; then placing .the headlight with the axis of the mirror Patented Aug. 7, 1917.

This requirement 1s best metby placing'the lamp. with the tip a crossed beam. With either of these adportion of the light which shines above the horizontal plane through the lamp is wasted and in addition serves to blind any person who may be on the road looking toward the approaching vehicle.

Many devices have been proposed to reduce the blinding effect, but practically all of them are objectionable in that they of necessityreduce much of the useful light at the same time that they reduce the blinding effect.

My experiments have shown thatthe' light I which comes directly from the lamp, Wlthn out having first been reflected from the mirror, causes little or no blinding effect; therefore my device is so designed as to deflect the reflected raysjof. light from the objectionable direction to a useful direction without affecting the direct rays of light to any marked degree.

When the lamp 1s adjusted with the major portion of the filament back of the focus of the reflector the beam isdivergent and the objectionable part is that which comes from the upper part of the reflector. When the lamp is adjusted with the major portion of Fig. 3 shows the relation of the headlight front to the lamp and reflector.

Figs. 5 and 4; show the directions of the light rays and forms of lighted field produced by the use of the fronts shown in Figs.

' edges inclined toward each dther to refract 1 and 2.

Referring tosFigs. l and 2: The device consists essentially of a transparent headlightfront with the lower portion B of'plane glass and the upper'portion A of prismatic glass; the p'rism's' ofthe two quadrants being inclined in. opposite directions and having their bases down. Afront of this kind is placed over the opening of a. parabolic mirror R-Fig. 3, having a lamp L placed so that a portion of the filament is at the focus of the mirror with the major portion between the mirror and its focus.

When adjusted in this waythe lighted field will be of essentially one of the shapes shown in Fi s. 4 and 5; depending on the inclination 0% the prisms with respect to the horizontal plane through the lamp and their optical angle. It is essential that the prisms have their bases down; but they may be made integralwith the'rest of the headlight front or infseparate pieces. I

-- The optical angle is determined in ac- I cordance with the well known laws for the refraction of light and is preferably such that none of the light reflected from the mirror is directed above the horizontal plane through the axis of the reflector.

A front of the type shown in Figs. 2 and 4 is used where it is desired to illuminate a broad field at a relatively low intensity and one of the formshown in Figs. 1 and 5 where it is desired "to illuminatea narrow field at. a'high intensity. In each of these fig- Y tires the lighted field marked a receives its light through that portion of the front marked A, that marked a through that portion of the front marked A and thatv 'must be down in each case.

- Witnesses:

reserve Y marked l through that portion of thetom. This is not the equivalent of turning the front over; for the bases of the prisms Having described my invention, I claim the following as new and ask for Letters Patent thereon:

1. A headlight front, of transparent material, having one plane sector, and two similar sectors composed of prisms with their spreading beam of light, in which the lower portion is plane and the. upper portion is composed of two mutually inclined sets of risms, with the bases down, so as to deect the light received from theupper portion of the mirror to a, direction below the horizontal' v I 3 .3. A lens for headlights comprising a plane portion and a prismatic portion, said prismatic portion having a plurality of sets of refracting prisms inclined toward each other to refractthelight downwardly.

l. A lens for headlights comprising a lower plane portion and an upper prismatic portfion, said prismatic portion having a plurality of sets of refracting prisms mclined toward each other to 'refract the light down-.

wardly. Y

5. A lens for headlights comprising a plane lower sector, and two similar upper sectors composed of refracting prisms with their edges inclined toward each other to refract the light downwardly.

6. lens for headlights comprising a plane lower portion and two similar upper portions composed of refracting prisms with their-bases down and with their edges incline'd downwardly towardeach other to refract the light downwardly. y

' ARTHUR H. FORD.

J.B.H1LL,- H. G.MILLER. 

